Lead alloy



R. S. DEAN LEAD ALLOY Filed June 29. m

DecQG, 1932.

Patented Dec. v6, 1932 UNITED STATES PATENT/orner.

REG-INALD SCOTT DEAN, OF RIVERSIDE ILLINOIS, ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEWYORK LEAD ALLOY Application led June 29, 1928. Serial No. 289,145.

This 'invention relates to lead alloys, articles made therefrom, andmethods of producing and/or treating such alloys and articles, and moreparticularly to alloys of lead and calcium, extruded articles madetherefrom, and methods of producing and/or treating such alloys andarticles.

An obj ect of the invention is to provide alloys of lead and calciumhaving some or all of the properties of extreme hardness, high tensilestrength, great resistance to failure from fatigue, large percentageelongation, excellent resistance to corrosion, and great stability atatmospheric temperatures.\

Another object of the invention is to provide articles made of alloys oflead and calcium, particularly electrical cable sheaths made of suchalloys.

Additional objects of the invention are to provide simple, eective, andexpeditious methods of producing and/ or treating alloys of lead andcalcium and articles made from such alloys resulting in and havingdesired physical and mechanical properties.

In accordance with the general features of the invention as embodied inone speciic form thereof, a quantity of calcium is alloyed with asufficient quantity of lead to produce an alloy containing less than 1%calcium and the alloy caused to solidify. The solidified alloy is heatedat a temperature suiciently high and for a suiiiciently long period oftime to cause substantially all of the resulting solute constituent toenter solid solution in the lead, and the alloy is then cooled from anelevated temperature at a suiiiciently rapidrate to cause some of thesolute constituent to remain in the lead in the form of a supersaturatedsolid solution, after which the alloy is caused'to assume a more stablestate by aging. In the manufacture of articles, such as cable sheaths,from an alloy of the type just described, an article may be formedtherefrom and then the formed article subjected to the above outlinedheating, cooling and aging operations, or else the'alloy may be iirstred'uced to the form of a solid solution and an article producedtherefrom While the alloy is hot, after which the hot article Awith thisinvention, advantage is taken o is cooled and aged'in the mannerdescribed above.

.The above described and other objects and features of the inventionwill be apparent fromthe following detailed description of oneembodiment of the invention, taken in connection with the accompanyingdrawing, in which Fig. 1 is a equilibrium diagram of the leadrich end ofthe lead-calcium system;

Fig. 2 is a diagram showing the comparative tensile strengths of alloystreated in accordance with this invention and alloys not so treated, and

, Fig. 3 is a diagram similar to .that shown in Fig. 2 showing thecomparative percentage elongations of treated and untreated alloys.

Referring now to Fig. l of the drawing, the curves shown thereinrepresent the loci ofthe points at which transformations in the physicalconditions of lead-rich alloys of lead and' calcium occur. In thediagram shown in Fig. l, the temperatures at which the transformationsoc'curare plotted as ordinates and the percentage compositions of thealloys in which theitransformations occur are plotted as abscissae. Thecurve ABC 'in the diagram is a liquidusl curve from which the meltingpoints of the various lead-calcium al-l loys may be obtained, while thecurve DE represents the solubility in lead of the solid soluteconstituent separating out with the lead when the alloys solidify. Froman examination of the diagram it will be seen that the solubility of thesolid solute constituent in lead varies with the temperature, the solidlead dissolving about .1%` of the calcium at 330 C. and less than .02%at room tempera-` ture or lower temperatures. In accordance the abovedescribed characteristics of leadrich alloys of klead and calcium toroduce alloys having enhanced properties and to produce articles, suchas cable sheaths, from these alloys. l e v Although it is not known withcertainty just what the solution of the lead and the i soluteconstituent comprises, it is believed that the calcium combineschemically with a part of the lead yto form a. compound having theformula Pb3Ca which enters solid solution in the remainder of the leadand separates out as a di'stinct constituent under certain conditions.In any event, whether or not such a, compound is found, the calcium,either combined or uncombined chemically with a part of the lead, entersinto solid solution in the lead. The theory upon which the processesdescribed below are based is the same regardless of whether the calciumis free or combined and it is to be understood, therefore, that in thefollowing description and annexed claims when it is stated that thesolute constituent or the calcium is caused to enter solid solution inthe lead, these terms are intended to mean either combined or uncombinedcalcium as the case may actually be.

In practicing one method of producing alloys in accordance with theinvention, a quantity of calcium falling within the range y bounded bythe maximum amount of calcium which will enter solid solution in lead atany temperature at which the resulting alloyis a solid and the amount ofcalcium which will be retained in solid solutionin lead at roomtemperature (02% to .1% calcium) is alloyed with lead and the resultingalloy caused to solidify. The solid alloy is then heated at atemperature sutliciently high to cause the calcium to enter solidsolution in the lead, which temperature maybe determined by referring tothe diagram shown in Fig. l of the drawing, and the heating is continueduntil substantially all of the calcium has entere into a substantiallyhomogeneous solid solution in the lead. The alloy is then cooled from anelevated temperature at a rate sulficiently rapid to insure theretention of some of the calcium in the lead in the form I of asupersaturated solution, (after which the alloy is caused to assume amore stable state by aging. The percentage of calcium employed and thetemperatures at which the heating, cooling and aging ste s are practiceddepend upon the characteristics desired in .the nished product and maybe deter'- mined by reference to Figs. 2 and 3 of the drawing.

Referring now to Fig. of the drawing,

which illustrates the Lcomparative tensile strengths of alloys treatedin accordance with the invention; and alloys not so treated,

thec'urve F'represents the tensile strength of the various alloys, Whosecompositions are indicated as abscissae, which have been heated at atemperature of approximately 320 C. untila substantially homogeneoussolid solutionwas produced and quenched from the temperature of 310 C.to room temperature and aged at room temperature, while the curve Gillustrates the tensile strengths of corresponding alloys which havebeen slowly cooled from 310 C. to room temperature so that practicallyno supersaturation of the solution of the solute constituent in the leadresults. Itv will be seen by reference to Fig. 2 that the alloys treatedin accordance with the invent-ion possess considerstrength reaching ahigh value when an alloy containing about .1% calcium is employed. Fromthis it will be evident that great tensile strength in the treatedalloys results Lvwhen the maximum amount of calcium which will entersolid solution in lead at any temperature at which the resulting alloyis a solid is employed.

Referring now to Fig. 3 of the drawing which illustrates the comparativepercentage elongations of alloys treated in accordance with theinvention and alloys not so treated, the curve H represents thepercentage elongations in six inches of alloys which have been formedinto a solid solution, reduced tof afs'ipersaturated solid solution andaged, while the curve I represents the percentage elongations ofcorresponding alloys which have been produced in such a manner that varylittle, if any, supersaturation of the solid solution results. As ageneral rule, the percentage elongation of metals decreases rapidly withincreased tensile strength and v it might be expected that lead-calciumalloys of increased tensile strength would exhibit low percentageelongations. However, from an examination of these curves it will beapparent that the percentage elongations of the treated alloys, Whileless than those obtained in the untreated alloys, are not sufficientlyless to materially decrease the usefulness of the treated alloys for themanufacture of articles, such as cable sheaths. case of the tensilestrength, a. high percentage elongation -results when the maximumkamount of calcium is employed which will enter solid solution in leadat any temperature at which the resulting alloy is a solid, namely about.1% calciun If an` alloy of a particular tensile strength and percentageelongation is desired, these characteristics may be obtainedby employingan alloy having the composition corresponding to the particularcharacteristics dcsired. For instance, if it is desired to produce analloy having a tensile strengthhof about 7000 pounds per square inch anda percentage elongation of about'40%, approximately .1% calcium isalloyed with lead and the resulting alloy is reduced to a solid state.The solid alloy is then heated at a temperature between 310 and 325 C.,which is the temperature necessary to cause this quantity of calcium toenter solid solution in lead, and the heating is continued untilsubstantially all ofthe calcium has entered solid solution in the lead.If great tensile strength is de- As in the lead throughout which aresubstantially uniformly dispersed a large number of minute particlescontainin calcium and it is believed that the en ianced properties whichsuch alloys possess result from the wide dispersion of these particlesand the extreme minuteness of the particles. It is import-ant,therefore, that the aging step be carried on at a temperaturesufficiently low so that little agglomeration of the finely dispersedparticles results, and it has been found that little agglomerationoccurs when the alloy is aged at a temperature below 150 C.

By practicing the above outlined method, alloys having very desirableproperties may be produced. For instance, alloys having a tensilestrength from 4000 to 7000 pounds per square inch, a percentageelongation ofgfrom 25 to 40% and a fatigue limit of from 800 to 1900pounds per square inch, may be obtained by following the above outlinedprocess. @ther advantageous properties of such alloys are theirresistance to chemical corrosion and their extreme stability of physicalproperties at atmospheric temperatures.

The above enumerated properties of alloys produced in accordance withthisinvention are very desirable in extruded articles, par- -ticularlysheaths for electrical cab-les, and

the above described process provides an eX- cellent means for producingsuch articles. For instance, in the manufacture of electrical cablesheaths, a lead-calcium alloy of the composition necessary to give thetensile strength, percentage elongation, etc., desired in the finishedsheath is produced, and thesolid alloy then 4heated and extruded in theJform of asheath surrounding an electrical cable under such conditionsthat the alloy.

making up the sheath as extruded will be in the form of a substantiallyhomogeneous solid solution. The alloy is then cooled at a ratesuiiiciently rapid to insure the retention of some of the soluteconstituentin a supersaturated solutionin the lead and the sheath thenaged to cause a dispersion of a solute constituent throughout the leadin the form of minute particles. Electrical cable sheaths made inaccordance with theinvention have proven to have characteristics farsuperior to those made of other alloys commonly used in the manufactureof cable sheaths, and consequently sheaths made in accordance with theinvention will be much more eective under service conditions than thoseheretofore known to the art.

It is, of course, to be understood that the methods outlined above andthe articles and alloys produced by practicing these methods are merelyillustrations of useful embodii ments of the invention and the inventionis limited only by the scope of the annexed claims.

What is claimed is 1. A method of producing improved alloysn of lead,which consists in alloying calcium therewith, heating the alloy to formasolid solution, cooling the alloy to produce a super# saturated' solidsolution, and aging the alloy to cause the dispersion of minuteparticles containing the calcium substantially uniformly throughout thelead.

2.: A method of producing improved alloys of lead, which consists inalloying calcium therewith, heating the alloy to form the same into asubstantially homogeneous solid solution, cooling the alloy from anelevated tem-r perature at a rate suiiciently rapid to insure theretention of calcium in the lead in the form of a supersaturatedsolidsolution, and

aging the alloy to cause it to assume a more stableistate.

3. A method of producing improved lead alloys, which consists inalloying with lead a quantity of calcium falling withinthe range boundedby the maximum amount of calcium which will enter solid solutions inlead at any temperature at which the resulting alloy is a solid and theamount of calcium which will remain in solid solution with lead at roomtemperature, forming the resulting alloy into a solid solution, reducingthe alloy to a supersaturated solid solution, and aging the alloy tocause it to assume a more stable state.

4. A method of producing improved alloys of lead, which consists inalloying from .02 to .1% calcium therewith, forming the alloy intoasupersaturated solid solution, and aging the resulting alloy to causethe dispersion of 4minute particles containing the calcium Vsubstantially uniformly throughout the lead.

5. A method of producing improved alloys of lead, which consists inalloying about .1% calcium therewith, forming the resulting alloy into asolid solution, reducing the alloy to a supersaturated solid solution,and aging the alloy to cause it to assume a more stable state. f

6. An alloy of leadaud'calcium, characterized by the presence of minuteparticles 'containing the calcium substantially uniformly dispersedthrough the lead, the metallurgical structure being formed by heatingthe alloy td form it into a solid solution, reducing the alloy to asupersaturated solid solution, and aging the alloy.

7 An alloy of lead and calcium containing a quantity of calcium fallingwithin the yiso range bounded by the maximum amount of calcium whichwill enter solid solution in lead at any temperature at which theresulting .alloy is a solid and the amount of calcium 5 which will beretained in solid solution in lead at room temperature, andcharacterized bythe presence of minute particles containing the'calciumsubstantially uniformly disp persed throughout the lead, themetallurgical structure being formed by heating the alloy to form itinto a solid solution, reducing the alloy to a supersaturated solidsolution, and

. aging the alloy.'

8. An alloy of lead and calcium containing from .02 to .1% calcium, andcharacterized by the presence of minute particles containing the calciumsubstantially uniformly dispersed throughout the lead, the metallurgicalstructure being formed by heating the alloy y to form it into a solidsolution, reducing the alloy to a supersaturated solid solution, andaging the alloy.

9. An alloy of lead and calcium wherein the calcium is uniformlydispersed having a tensile strength of from L1000 to 7000 pounds persquare inch, a percentage elongation greater than in six inches, and afatigue limit of from 800 to 1900 pounds per square inch, themetallurgical structure being formed by heating the alloy to form itinto a solid solution, reducing the alloy to a supersaturated solidsolution, and aging the alloy.

10. An age-hardened alloy of lead and calcium containing a quantity ofcalcium falling within the range bounded by the maximum amount ofcalcium which will enter solid solution in lead at any temperature atwhich the resulting alloy is a solid and the amount of calcium which,will be retained in solid solution in lead at room temperature, themetallurgical structure being formed by heating the alloy to form itinto a solid solution, reducing the alloy to a supersaturated solidsolution, and aging the alloy.

l 11. An age-hardened alloy of lead and cal- -cium containing from .02to .1% calcium, the

metallurgical structure being formed b heating the alloy to form it intoa solid so ution,

reducing the alloy to a supersaturated solid 73 solution, and aging thealloy.

Y, 12. An age-hardened alloy of calcium and lead containingsubstantially .1% calcium, the metallurgical structure being formed byheating the alloy to form it into ra solid solu- 14. A method ofproducing improved al-I loys of lead, which consists -in alloyingcaltion,'reducing the alloy to a supersaturated` cium therewith, heatingthe alloy to form the same into a substantiallyhomogeneous solidsolution, reducing the alloy to a supersaturated solid solution, andaging the alloy.

15.` A method of producing improved alloys of lead, which consists inalloying calcium therewith, heating the alloy at a temperature slightlybelow the fusion temperature thereof until a substantially homogeneoussolid solution is produced, reducing the alloy to a supersaturatedsolidsolution, and aging the alloy.

16. A method of producing improvedalloys of lead, which consists inalloying calcium therewith, heatingl the alloy at a temperature of 280C. to 320 C. until a sub-y stantially homogeneous solid solution isformed, coolingthe allow at a rate suii'iciently rapid to insure theretention of calcium in the lead in the form of a supersaturated solidsolution, and aging the alloy to cause it to assume a more stable state.

17. A method olf-.producing improved lead alloys, which consists inalloying with lead a quantity of calcium falling with the range boundedby the maximum amount of calcium which will enter solid solution in leadat any soy temperature at which the resulting allow is a solid and theamount of calcium which will remain in solid solution in lead at roomtemperature, heating the alloy to form a solid solution, cooling thealloyLto produce a supersaturated solid solution,- and aging the alloyto cause the dispersion of minute particles containing the calciumsubstantially uniformly throughout the lea 18. A method-of producingimproved alloys of lead, which consists in alloying from .02% to .1%lcalcium therewith, heating the. resulting alloy to form it into a solidsolution, reducing the valloy to a supersaturated solid solution, andaging the alloy to cause it to assume a more stable state.

19. A method of producing improved alloys of lead, which consists inalloying there-y with substantially the maximum amount of calcium whichwill'cnter solid solution in lead at any temperature at which theresulting allo;r is a solid, heating the alloy to form a solid solution,cooling the alloy to form a 115 `supersaturated solid solution, andaging the alloy to cause the dispersion of minute partiy. clescontainingthe calcium substantially uniformly throughout the lead.'

20. A method ofcproducing improved al '120 loys of lead, which consistsin alloying therewith substantiallyr the maximum amount of calcium whichwill enter solid solution in lead at any temperature at which theresulting alloy is a solid, heating the resulting alloy to form intoa-solid solution, reducing the alloy to a supersaturated solid solution,and aging the alloy to cause it to` assume a more stable state.

21. A method of producing improved alloys of lead, which consists inalloying about .1% calcium therewith, heating the alloy .to form a solidsolution, cooling the alloy to form a supersaturated solid solution, andaging the alloy to cause the dispersion of minute particles containingthe calcium substantially uniformly throughout the lead.

22. An alloy of lead and calcium containing substantially .1% calcium,and characterized by the presence of minute particles containing thecalcium substantially uniformly dispersed throughout the lead, themetallurgical structure being formed by bringing the alloy into solidsolution, reducing the alloy to a supersaturated solution, and aging thealloy.

23. The method of producing a lead alloy, which comprises alloying witha quantity of lead a quantity of calcium greater than is soluble thereinat room temperature, maintaining the alloy at an elevated temperaturebelow its melting point to cause the calcium to enter solidsolution inthe lead, quickly reducing the temperature of the alloy to form asupersaturated solid solution, and aging the alloy to cause dispersionof minute particles containing calcium substantially uniormly throughoutthe lead.

In witness whereof, I hereunto subscribe my name this 7th day of June,A. D. 1928.

REGINALD SCOTT DEAN.

